Core construction for electromagnetic apparatus



Dec. 2, 1947. L. MAUERER CORE CONSTRUCTION P' OR BLEC'I'ROIAGNBTIC APPARATUS 2 ShutsBSheot 1 Filed Jan. 26. 1944.

L. MAUERER Dec. 2, I947.

CORR CONSTRUCTION FQR BLBCTROIAGHBI'IC AIPAMTUS Filed Jan. 26. 1944 2 shoots shuot 2 two I directions:

approaching that Patented Dec. 2, 1947 cons CONSTRUCTION FOR ELECTRO- MAGNETIC APPARATUS Leopold Mauerer, Chicago, Ill., assignor to J efferson Electric Company, Bellwood, 111., a corporation of Illinois Application January 26,1944, Serial No. 519,732 j 19 Claims. (01. 175-356) This invention relates to improvements in core construction for electromagnetic, apparatus and .in particular to an improved clamping means which permits a, core, such as a transformer or reactor core to be made inseparate sections, and which exerts a clamping action on the core in laterally, to press, the laminations together; and longitudinally, to hold the core sections in that closely abutting relationship which is desirable for establishing a satisfactory magnetic path. An object of this invention is to provide a single clamping means'for a sectional laminated magnetic structure which acts both laterally and longitudinally, and which serves not only to press the laminations of each section together, but to hold the sections in, abutting relationship with each other.

providing that the laminations are, stamped to close tolerances. part to the use of This is believed to be due in a'singie clamp which acts in both directions so that the lateral pressure is incore structure each pair of laminations is not separately held in abutting relationship by any degree of press A further object is. to provide an improved core clamping means which bears laterally on each core section at or about the end thereof so, as to minimize any tendency of the lamlnations to spread, as one section is forced into abutting engagement with another. I

A still further object is to provide an improved core clamping means which bears on each section separately in a manner so tain amount or lateral adjustment as the sections are forced into abutting relationship with each other.

Due to the closed circuit design of transformer cores, reactor cores and the like, it has been the practice to make each lamination in two pieces,

- and assemble them into the pro-wound coil, the

layers of laminations being so arranged that the joints of adjacent layers are staggered.v This provides a unitary'core structure, and is referred to as one formed from interlaced laminations.

The building up of such a core StlllCtLlIBhOW- ever is a time consuming task, and it is evident that the cost of assembling a transformer can be materially reduced if laminations of like shape can be stacked together in one section and iaminations of another shape stacked together into a, different section, and the two sections clamped together. I 7

"Practical objections to the adoption of such a construction arise from the fact that it is difficult to urge two sections into suiiiciently intimate contact as to provide a core having a reluctance of a core formed from interlaced laminations. It hasbeen found however creased gradually as the longitudinal pressure is increased." This gradual increase of pressure will permit the sliding or longitudinal displacement .of one lamination with respect to an adjacent lamination so as to bring substantially all of the pairs of laminations intoclosely abutting contact, thereby reducing the reluctance of the core to a point where it approximates the reluctance of an interlacedcore structure. It will benoted in thisconnection that the abutting relationship of 'a manually built up interlaced is notperfect for the reason that sure.

I vide an improved core construction wherein the as to provide a cerpartly in section;

that the use of such a sectional core in combination with the type of clamp herein described and shown gives eminently satisfactory results,-

,tudinal and lateral Fig. 1;

core is built up in sectionsandthe sections are assembled in abutting relationship and maintained therein in a manner to reduce the over all reluctance of the core to a minimum.

g A further object isto provide a magnetic core asembly which, due to the relativelyhigh longi pressures exerted thereon, is not subject to any variation in the air gap between abutting sections, and is free from hum.

, A still further object is to provide a sectional laminated magnetic core assembly in combinw tion with lateral clamping means engaging each section separately so that the laminations of each section will be pressed together with substantially the same degree of pressure even though the sections maynot be of identical thickthe accompanying of this disclosure,

and in which like reference numerals refer to like parts:

Fig. l is an elevation of ment of this invention;

Fig. 2 is an end view of the unitgshown in F '1;

Fig. 3 is an enlarged detail a preferred embed! of Fig. 2, which is Fig. 4 is an enlarged detail of Fig. 2; V Fig. 5 is a section taken along line 5-4 of the reactor coil l8,

detail of Fig. 8, partly in detail of a modification,

' As the nuts and It which is oi'ten referred to as a ballast. This unit is essentially a transformer together with two reactor 'coils, and is used in connection with gaseous conduction tubes. The ballast includes a primary and secondary coil l8 and two reactor coils I1 and I8. Suitable leads for these coils are shown; The transformer core I! is composed of E-lamlnatlons and I -laminations 2| which are interlaced, as shown in Fig. 2. The

reactor core 22, for the reactor coil I1, is formed of E-laminatlons 23, and the reactor core 24, for

is formed solely from E-laminations 25. It will be seen that the transformer core l9, and reactor cores 2'2 and 24 comprise three separate sections which are held in end to and relationship, there being a butt joint 26 between the cores l9 and 22, and a butt joint 21 between the cores l9 and 24.

These'separate sections are held in end to end relationship by means of clamps 28 and 29. In-

- asmuch as these clamps are identical to each other, only clamp 28 will be described in detail..

Clamp 28 comprises astrap 38, end pieces 3| and 32, and spacers 33. The strap 20 is tensioned around the three core sections and at its ends is provided with bolts 34 and 35 which may be suitably secured to the straps by weld'ng. The end piece 3 l is in the form of a channel, and the bolts 34 and 55 pass through czrtain apertures which have been formed in the connecting or web portion of the channel by striking out lips 35 and 31. The outer ends of the bolts are engaged by nuts. and 38 which react against the connecting portion of the channeled end piece II. It will be noted in Fig. 3 that the bolts 34 and are disposed at an angle to each other and that the connecting portion has been formed to provide two angularly disposed portions 40 and 4i, the plane of each of these being perpendicular to the axis of the bolts 34 and 35 respectively, so as to form a seat for the nuts 38 and 39.

The end piece 32 is also in the form of a channel whereof the connecting portion has been cut away to form edges 42 and 43, around which edges the strap is bent.

The spacers 33 are disposed along each leg of the strap at points opposite the butt joints 26 and 21. The spacers are identical in construction, and each is provided with feet 44 and 45 which are disposed at an angle to each other so that as shown in Fig. 4, foot 44 will bear against the reactor core section 22, and foot 45 will bear against transformer core sectioh 19. The spacers are rookingly mounted on the strap 35 by means of lugs 46 and 41 which are struck up and around the strap 30. The edges of the strap 30 may be notched as shown (at 48) in Fig. 5 so as to provide an interlocking engagement with the lugs and 41, thereby maintaining the spacers 33 in their proper position opposite their respective butt joints. 7

In operation, after the coils have been assembled with respect to the core sections. they are placed in end to and relationship, and the clamps 25 and 25' are slipped over the assembled unit. are tighten'ed. the bolts 54 and I5, and the strap 50 will be drawn up which will have a dual eflect of urg ng the core sections into intimate relationship with each other at the butt joints 25 and 21, and of pressingthe laminations of each section together laterally. There may be slight irregularities in the alignment of the laminations'of one stack or core section with the'laminationsof another stack, which irregularities, as the strap is tightened up, may cause a slight lateral shifting of one core section with respect to another. This lateral shifting is permitted by means of the rocking mounting of the .spacers 52 on the strap 24.

It will be noted that the edges 42 and 42 of the end piece 22 are offset inwardly beneath the extended surface plane of the core section 24. This construction is shown in detail in Fig. 6. This permits the strap to contact the corner of the core section 24 so that the laminations will be pressed together at their lower edge, just as they are pressed together at their upper edgeby the feet of the spacers 32. This same effect is secured with respect to the end piece II by means of the lips 36 and 31 which tend to determine the position of the bolts 24 and 25. Inasmuch as the bolts do not possess a flexibility comparable to that of the strap 50 which can actually be bent around the lower corner of the reactor core section 24 to a slight extent, the lips "land 41 are slightly resilient so that they may give slightly to permit the proper angular alignment of the bolts with the legs of the strap ll.

vIt will be noted that the edges of the side members of the channeled end pieces 2| and I2 bear against the lamination stacks and serve to align them as the nuts 25 and II are being tightened. In other words, if, in the original stacking, the edges of the laminations are not even, these irregularities will tend to be straightened out as the straight edges of the end pieces are brought to bear against the laminations with considerable I section is merely a stack of laminations of identical size and shape. The two sections are held in abutting relationship by means of clamps 55 and 56 which are substantially identical. Only clamp 55 will be described herein.

This form of clamp comprises a strap 51 in the form of a loop, the ends being spot welded to each other as shown at 55. End pieces 59 and 40 are disposed between the ends of the core and the strap, the end pieces providing straight edges for the proper alignment of the separate laminations as described in connection with Figs. 1 to 6.

Each of the end pieces consists of a channel member in which the connecting or web portion is disposed in contact with the core, and the edges of the said pieces contact the strap 51. End

piece 55 receives wedges 55 and 44, the former sliding on the web portion of end piece 55, and the latter being confined between the strap 51 and the wedge 63. It will be seen that asv these wedges are forced into place, the strap 51 will be tensioned. Spacers ll. identical to the spacers II, are provided, one pair 01' which straddles the butt Jointv between the core sections '3 and I! as shown in Fig. 8. The other pair oi spacers engages section 54 atan intermediate portion to prevent buckling. I

In the modification herein disclosed, the strap I1 is apertured as indicated at 62, and the end the clamp acts in two directions; that is, it compresses the iaminations, and it urges the core sections in intimate engagement with one another. In the reactor unit of Figs. ,l to 6, aspacer may be inserted in the butt joints 2. and 21, if desired, the spacer being of suitable nonmagnetic material, to increase the air gap eilect; however,

whether it be designed specifically for use as a transformer, a ballast, a reactor, or other type of apparatus.

I claim:

1. A'transtormer core comprising a plurality of sections, each section consisting or a stack of laminatlons, and clamping means surroundim; said core to maintain said sections in abuttin relationship, said clamping means including a tensioned strap and spacer members disposed between said strap and the. top and bottom lami nations of each core section at points. adjacent thexjoint therebetween to'ccmpress said lamiit will be noted that the middle legs of the reactor cores 22 and 24 terminate. short oi contact with the transformer core i9, thereby providing an air gap which introduces the desired reluctance in the reactors without resorting to the insertion of the spacers.

A further modified form of means for tightening up the clamp is shown in Figs. 10 and 11.

.The strap 10 is provided with free ends 1i and I2, each of which is apertured to receive a wedging member 14. An end piece 11, similar in form to the end piece '32, is interposed between the wedging member 14 and care 11. a The wedging member is so shaped that it presents cam surfaces 15 at either end, which rise as one approaches the middle of the wedging member 14. Inwardly adjacent to these cam surfaces 1! are arcuate portions 18, the radius of which approximates the distance between the arcuate surface and the corner 18 of the core around which the ends 1| and 12 may be bent.

In assembling, after the strap 10 has beenpo- I sitioned around the core 11, the end piece 13 is inserted between the end portions H and 12, and then these end portions may be spread sumclentiy so that the ends of the wedging member H may beinserte'd in the apertures provided I therein. Then as the end portions 1i and 12 are forced toward each other, the strap will be progressively tightened until the high point oi the cam surfaces 15 are reached. Further forcing 01' the end portions H and "toward each other will cause the strap to be bent around the corners 18 of the core 11, thereby causing a clamping action to be exerted on the end of the core. Inasmuch as the surfaces 16 are, arcuate with the corners 18 as a center, there will be no j tendency for the end portions 1i and 12 to straighten out, but it will be noted that this arcuate portion does resist any tendency of the ends to spring outwardly in a lateral direction, as contrasted with a rotational movement. Thus the clamping means is effectively locked.

Although only preferred embodiments of this invention have been described and illustrated herein, it will be understood that various modiiications and changes may bemade without departing from the spirit of this invention. The drawings and the foregoing description are illus- ,nations laterally, said spacers each having two,

bearing points, one or said points bearing against the iaminations of one core section and the other bearing against the laminations of the other core section, thereby preventing spreading of the laminations at the abutting edges of each stack.

2. A transformer core comprising-adjacent sections, each section consisting of a stack ot-laminationsatensicined strap surrounding said core and maintaining said sections in end to end relationship, and spacer members disposed between said strap and said core and having twoseparate bearing surfaces, each of which bears on one oi said adjacent sections at points adjacent the Joint therebetween to compress said laminations lat erally. a

. 3. A transformer core comprising adiacent sec tions, each sectionconsisting or a stack of laminations, a tension'ed flexible member surrounding said coreandrmaintaining said sections in end to end relationship, and a spacer member mounted on said tensioned flexible memberand having two points of engagement with said core, and disposed so that said points of engagement bear against the top laminations or adiacent sections.

4. A transformer; core comprising adjacent stacks of laminations. and clamping means one rounding said core and maintaining said secti in abutting end to and relationship. said a ing means including atensioned strap and spacer members disposed between said strap and said core at points opposite the joints between adiacent stacks, said spacers having two separate points of engagement, one for each of said adia cent stacks,.so that each spacer bears on both of said adjacent stacks to compress said laminations laterally. v

5. A transformer core comprising adjacent stacks of laminations, and clamping means surrounding said core and maintaining said sections in abutting end to end relationship, said clamp ing means including a tensioned strap and spacer members rockingly mounted on said strap and having two points oi engagement with said core. and disposed so that said points of engagement bear against adjacent stacks whereby a slight lateral adjustment ofthe stacks may be effected spacer disposed between said strap and the top lamination oioneoi said sections, and a second spacer disposedbetween said strap and the hot tom lamination oi said section at a point substantialiy opposite said first mentioned spacer, both of said spacers being rockingly mounted on said strap, and means to tension said strap to force said two sections together and to compress the laminations between said spacers.

7. A transformer core comprising two laminated core sections disposed in abutting relationship, a strap disposed around said core sections. two spacers disposed between said strap and said core sections and each bearing on both of said sections at oppositely disposed points, end pieces disposed between said strap and the ends of said core and bearing edgewise on the laminations of each of said sections, so as to cause sliding longitudinal displacement of a projecting lamination with respect to an adjacent lamination when said strap is tensioned, and means to tension said strap so as to cause said laminations to be compressed gradually, thereby permitting edgewise adjustment of said laminations with respect to said end pieces before said strap has been tensioned to any great extent wherein said laminations are clamped together with a force sufficient to prevent further displacement thereof.

8. A clamp for a laminated transformer core comprising a strap disposed around the core, and an end piece interposed between said strap and the edges of the laminations of said core, said strap being tensioned around said end piece so that it engages the corners of said core to com press said laminations, and said end piece bein extended beyond said strap so as to engage the edges of all of said laminations.

9. A clamp for a laminated transformer core comprising a strap in the form of a loop surrounding said core, an end piece interposed between said strap and the edges of the laminations of said core, said strap being disposed around said end piece in such a manner that it engages the corners of said core to compress said laminations, and said end piece being extended beyond said strap so as to engage the edges of all of said laminations, and cooperating wedges bearing on said end piece and on said strap for tensioning said clamp.

10. A clamp for a laminated transformer core comprising a strap disposed around the core, an end piece in the form of a channel bearing on the edges of the laminations of said core, the opposite walls of said channel being perpendicular to the end surface of said core, said strap being bent around said end piece so that it engages the corners of said core to compress said laminations, and said end piece being extended beyond said strap so as to engage the edges of all of said laminations, and cooperating wedges slidingly di posed within said channel and confined between the opposite walls thereof whereby said strap may be tensioned by sliding one wedge over the other.

11. A clamp for a sectional laminated trans former core comprising a U-shaped strap having threaded bolts secured to the free ends thereof, an end piece for cooperation with the open end of said strap and having apertures formed therein to receive said bolts, and nuts threaded onto said bolts and bearing against said end piece to tension said strap and to draw said end piece against the edge of said laminated core to align the laminations thereof, in combination with a spacer disposed between the strap and the core, said spacer bridging the joint between the sections of the core, and having two separate hearing points, one bearing on each section.

12. A clamp for a laminated transforme core comprising a U-shaped strap having threaded bolt portions secured to the free ends thereof, an

end piece in the form of a channel for cooperation with the open end of said strap, said channel having a. web portion spaced from the edges of said laminations and having apertures formed in said web portion to receive said bolt portions, said apertures being offset inwardly from the extended side surface planes of said core whereby said bolt portions are disposed at an angle to said planes and engage said core at its corners to compress the laminations thereof.

13. A clamp for a laminated transformer core comprising a U-shaped strap having threaded bolts secured to the free ends thereof, an end piece in the form of a channel for cooperation with the open end of said strap, said channel having a. web portion spaced from the edges of said laminations and having apertures formed in said web portion to receive said bolts, and resilient lips formed on said and piece and spaced from each other by a distance slightly less than the thickness of the core plus the bolts, and engaging said bolts to hold the same against spreading, and to maintain them in contact with the corners of said laminated core.

14. A clamp for a laminated transformer core comprising a strap adapted to be slipped over the core, and spacers secured to said strap for engaging the outer laminations of said core, said spacers being provided with two feet adapted to engage said core, and having lugs struck up from the connecting portion between said feet and embracing said strap.

15. A clamp for a laminated transformer core comprising a strap adapted to be slipped over the core and having notched edge portions, and spacers secured to said strap for engaging the outer laminations of said core, said spacers being provided with two feet adapted to engage said core, and having lugs struck up from the connecting portion between said feet and embracing said strap at said notched portions in interlocking relationship.

16. In a sectional laminated core structure for electromagnetic apparatus, clamping means for compressing said laminations and for urging the separate sections of said core structure in flux transmitting relationship, said clamping means comprising a. strap provided with spacer members engaging each section separately at points adjacent the joint therebetween, and end pieces disposed at opposite ends of said core structure and engaging the several laminations thereof, said strap being tensioned around one of said end pieces, and a wedge shaped tensioning device bearing against the other of said end pieces and engaging said strap for tensioning the same, said strap, at those portions thereof extending from a spacer member to one of said end pieces, being disposed at an angle to said laminations in such a manner as to engage the corners of said core structure and to compress said lamination.

17. A tensioning device for a core clamp which includes a strap disposed around two sides and an edge of a laminated core, the ends of said strap extendin beyond the opposite edge thereof, said tensioning device comprising a transverse member disposed parallel to said opposite edge of said core and reacting thereagainst, the ends of which member are received in oppositely disposed apertures formed in said strap, said transverse member including a. cam surface engaged by said apertured strap, said cam surface being continuous and comprising a rise portion and a dwell portion whereby said strap will remain in a tensinned condition after it has been bentamund a corner edge of said cora 18. A tensioningdevice for a core clamp which includes a strap-and aspaoer interposed between said strap and the side of a'laminated core, said tensioning. device comprising a transverse member disposed at an edge of said core andreacting thereagainsh'thea ends or which member are received in oppositely disposed apertures formed in said strap, said transverse member including a cam surface engaged by said apertured strap which has a high point with respect to said spacer and a descending portion inwardly adjacent thereto. all points on said descending portion being substantially equidistant from the nearest comer edge of said coreto permit said strap to be bent around said corner edge without substantially varying the tension thereon.

19. A clamp for a laminated sectional core to be used in electromagnetic apparatus, comprising i a U-shaped strap disposed about the core, the free ends of which extend beyond one edge of said core and are provided with perforations, and tensioning means for said strap comprising a member disposed parallel to said edge of said core and having ends adapted to be received within said perforations in strap engaging relationship, the remote portions of said ends being wedge shaped and each having a high point so as to cause said strap to be tensioned as the perforated portions thereof are forced together toward said high points, and the portions adjacent to said high points of said end member arcuately shaped with respect to the nearest corner of said core position.

LEOPOLD MAUERER.

REFERENCES CITED The following references are of record in the die of this patent:

UNITED STATES PATENTS Number Name Date 2,289,175 Boucher July 7, 1942- 1,686,513 Cady Oct. 9, 1938 2,029,983 Burke Eeb, 4, 1936 2,318,095 Putman May 4, 1943 461,135 Stanley Oct. 13, 1891 1,731,894 Frisch Oct. 15,1929 1,382,873 Wagner June 28, 1921 2,336,665 Boucher Oct. 12, 1943 2,367,927 Chubb Jan. 28, 1945 1,145,551 Burke July 6; 1915 2,381,369 Boucher Oct. 12311943 FOREIGN PATENTS Number Country Date 753,881 France Oct. 26, 1933 20,647 Great Britain Sept. 1902 427,792 Germany Apr. 19, 1926 440,008 Great Britain Dec. 18, 1935 

